Project Summary/Abstract Recent adolescent-based research shows that inferencing improves across grades 6-12, uniquely accounts for variance in sentence- and passage-level comprehension, and that individual differences in inferencing relate in a principled way to variations in reading comprehension for readers of all abilities (Barth et al., 2015; Barnes et al., 2015). These findings suggest that comprehension requires inferencing and that comprehension fails when readers do not possess relevant knowledge (i.e., availability) or slowly retrieve (i.e., accessibility) and integrate knowledge from text or semantic memory during reading (Kendeou, 2015). To date, only one study has examined the effects of knowledge availability and accessibility on inferencing among adolescents. To extend this limited body of research, this application requests three years of funding to conduct experimental studies designed to examine (a) the extent to which knowledge-base availability and accessibility relate to the accuracy and rate of constructing inferences using that knowledge (Aim 1) and (b) the extent to which retrieval practice (i.e., spaced practice testing) increases knowledge availability and accessibility and improves the accuracy and rate of forming inferences using that knowledge-base among middle grade readers (Aim 2). In addition, this proposal seeks to integrate investigative research into an undergraduate Honors Research Program by developing an investigative laboratory component that engages undergraduates in conducting applied research (Aim 3). The research design uses 558 students in grades 5-8. To address Aim 1, mixed effects explanatory item response models will fit to the trial-by-trial reading accuracy and speed data. Repeated measures analysis of variance models will address Aim 2 with analysis of variance models used for Aim 3. The expected outcomes of the proposed research include (a) understanding how knowledge availability and accessibility relate to inferencing among adolescent readers; (b) understanding the sources of inferencing difficulty; and (c) methods for improving knowledge availability and accessibility and inferencing to broadly implement in secondary grade classrooms.